FreedomPop on Thursday started taking preorders for its first product, an add-on sleeve that gives the iPhone 4G data capability.

The company, which is backed by Skype co-founder Niklas Zennstrom, is promising users who buy the $99 device upwards of 500 megabytes of free data use each month. The company isn’t building its own network, but is using data service to be provided by Clearwire and others.

Those who order the device being are told that it will ship by the end of the summer, though they can request a refund if they get tired of waiting.

“The timing couldn’t be better for our product,” said FreedomPop VP of Product Mauricio Sastre in a statement. “Carriers are throttling data and increasing prices and users are desperate for affordable alternatives. As the mobile industry flexes its joint oligopolistic power, we want to ensure that we are keeping them honest.”